Transmitter, Receiver, Transmission Method and Reception Method

Abstract

A phase relationship between signal sequences obtained by space-time-coding transmission signals is controlled so as to give a difference in peak power between the signal sequences to be transmitted from separate transmission antennas, and either one or both of the signal sequences are controlled so as to minimize a rate of a peak power of one of the signal sequences to an average transmission power of the signal sequences.

1 . A transmitter comprising:
 a plurality of transmission antennas;   an encoder that performs space-time-coding on transmission signals to generate signal sequences to be transmitted from the separate transmission antennas;   a phase controller that controls a phase relationship between the signal sequences obtained through the space-time-coding so as to give a difference in peak power between a first signal sequence of the signal sequences to be transmitted from a first transmission antenna and a second signal sequence of the signal sequences to be transmitted from a second transmission antenna;   a peak power measurement unit that measures peak power of the first and second signal sequences whose phase relationship has been controlled; and   a transmission power controller that controls a transmission power of either one or both of the first and second signal sequences based on a result of the measurement so as to minimize a rate of a peak power of one of the signal sequences to an average transmission power of the first and second signal sequences.   
   
   
       2 . The transmitter according to  claim 1 , wherein the transmission power controller decreases a transmission power of either one of the first and second signal sequences generating a higher peak power, while increasing a transmission power of the other signal sequence generating a lower peak power, the first and second signal sequences being given a difference in the peak power. 
   
   
       3 . The transmitter according to  claim 2 , wherein the transmission power controller controls the transmission power of the first and second signal sequences so that a sum of the transmission power of the first and second signal sequences is constant. 
   
   
       4 . The transmitter according to  claim 1 , wherein the transmission power controller controls the transmission power so as to satisfy predetermined conditions under which an orthogonal relationship between the first and second signal sequences is kept. 
   
   
       5 . The transmitter according to  claim 4  further comprising a transmission power control amount notifier that notifies a receiver receiving the first and second signal sequences of power control amounts for the transmission power satisfying the predetermined conditions. 
   
   
       6 . The transmitter according to  claim 1 , wherein the control on the phase relationship includes a phase control on sub-carriers on which the signal sequences transmitted from each of the transmission antennas are mapped. 
   
   
       7 . The transmitter according to  claim 1 , wherein the control on the phase relationship includes a phase control on orthogonal codes by which the signal sequences transmitted from each of the transmission antennas are multiplied. 
   
   
       8 . The transmitter according to  claim 1  further comprising:
 a signal exchanger that exchanges an element signal in the first signal sequence for an element signal of the second signal sequence or vice versa between the transmission antennas based on a relationship of magnitudes between the peak power measured by the peak power measurement unit so as to satisfy the predetermined conditions under which the orthogonal relationship between the first and second signal sequences is kept.   
   
   
       9 . The transmitter according to  claim 8  further comprising a signal exchange information notifier that notifies the receiver receiving the first and second signal sequences of whether or not the signal exchange has been done. 
   
   
       10 . The transmitter according to  claim 1  further comprising:
 a mapper that maps the first and second signal sequences whose phase relationship has been controlled onto separate sub-carriers; and   an inverse fast Fourier transform (IFFT) processor that converts the first and second signal sequences mapped on the sub-carriers into a time domain; wherein   the peak power measurement unit measures peak power of the first and second signal sequences converted into the time domain.   
   
   
       11 . The transmitter according to  claim 1  further comprising a peak suppressor that performs a peak suppression process on the first and second signal sequences having undergone the transmission power control. 
   
   
       12 . A receiver comprising:
 a receiver that receives a signal from a transmitter controlling a phase relationship between a first signal sequence transmitted from a first transmission antenna and a second signal sequence transmitted from a second transmission antenna of signal sequences obtained by performing space-time-coding on transmission signals so as to give a difference in peak power between the first and the second signal sequences;   a propagation path estimator that estimates propagation paths from the respective transmission antennas based on known reception signals from the respective transmission antennas;   a phase corrector that performs phase correction according to control information about the phase relationship on a result of estimation made by the propagation path estimator;   a propagation path compensator that performs propagation path compensation on a signal sequence received by the receiver based on a result of estimation corrected by the phase corrector to separate the signal sequence into signal sequences from the respective transmission antennas; and   a decoder that performs addition and subtraction on the signal sequences having undergone the propagation path compensation to decode the signal sequences.   
   
   
       13 . The receiver according to  claim 12  further comprising a power corrector that corrects power of the separated signal sequences according to power control amounts with which the transmission power have been controlled in the transmitter so as to satisfy that the predetermined conditions under which the orthogonal relationship between the first and second signal sequences is kept. 
   
   
       14 . The receiver according to  claim 12 , wherein the power control amounts are notified from the transmitter. 
   
   
       15 . The receiver according to  claim 12 , wherein the transmitter maps the first and second signal sequences whose phase relationship is controlled onto separate sub-carriers, converts the first and second signal sequences into a time domain, and transmits the first and second signal sequences; and
 the propagation path compensator performs the propagation compensation on each of the separate sub-carriers.   
   
   
       16 . The receiver according to  claim 12 , wherein the propagation path compensator performs an exchange control on reception signals to be subjected to the propagation path compensation according to whether or not an element signal in the first signal sequence and an element signal in the second signal sequence have been exchanged for one another between the transmission antennas in the transmitter so as to satisfy the predetermined conditions under which the orthogonal relationship between the first and second signal sequences is kept. 
   
   
       17 . A transmission method comprising:
 performing space-time-coding on transmission signals to generate signal sequences to be transmitted from separate transmission antennas;   controlling a phase relationship between a first signal sequence to be transmitted from a first transmission antenna and a second signal sequence to be transmitted from a second transmission antenna of the signal sequences obtained through the space-time-coding so as to give a difference in peak power between the first and second signal sequences;   measuring peak power of the first and second signal sequences whose phase relationship has been controlled; and   controlling transmission power of either one or both of the first and second signal sequences based on a result of measurement so as to minimize a rate of a peak power of one of the signal sequences to an average transmission power of the first and second signal sequences.   
   
   
       18 . A reception method comprising:
 receiving a signal from a transmitter controlling a phase relationship between a first signal sequence to be transmitted from a first transmission antenna and a second signal sequence to be transmitted from a second transmission antenna of signal sequences obtained by performing space-time-coding on transmission signals so as to give a difference in peak power between the first and second signal sequences;   estimating propagation paths from the respective transmission antennas based on known received signals from the respective transmission antennas;   performing phase correction according to control information about the phase relationship on a result of propagation path estimation;   performing propagation path compensation on a received signal sequence based on a result of propagation path estimation corrected through the phase correction to separate the received signal sequence into the signal sequences from the respective transmission antennas; and   performing addition and subtraction on the signal sequences having undergone propagation path compensation to decode the signal sequence.